The present invention relates to an apparatus for sensing the Schnarren phenomenon in a high pressure fuel injection line for an internal combustion engine.
Fuel injection systems for internal combustion engines are desirable because they provide high efficiency. Generally, such fuel injection systems comprise a fuel pump which supplies fuel at elevated pressure to a fuel injection valve. The valve is alternatingly opened and closed at proper timing in the engine operating cycle to inject fuel into the engine combustion chamber, thus producing pulsating fluid pressure in a line leading from the pump to the valve.
A problem which occurs frequently in the design and maintenance of fuel injected engines is the Schnarren phenomenon which is constituted by vibration of the fuel injection valve element at low values of fuel injection volume. This effect results in erratic fuel injection and substantially degraded operating efficiency.
In order to properly design and maintain a fuel injection system, it is necessary to accurately sense and measure the presence of the Schnarren phenomenon. However, apparatus for accomplishing this purpose has not been developed heretofore. Instead, the phenomenon has been sensed in a subjective manner by observing the fuel injection from a valve and/or listening to the sound produced by the valve during operation. The results of such evaluation naturally depend on the subjective determination of the observer and cannot be applied to a display unit, recorder, computer or the like for objective numerical analysis.